The invention relates to a cardiac pacemaker having a circuit arrangement for varying the pacing rate as a function of a measured value representing the stroke volume as recorded in the patient's body.
A pacemaker of this type is known from European Pat. No. (A) 00140 472. In a pacemaker of this type, it is difficult to optimize the setting of the heart rate for a given patient as a function of a value corresponding to the stroke volume, because cardiac characteristics vary individually from patient to patient.
For precise matching of pacemaker behavior to the individual, the nonlinear relationship between the cardiac output, the stroke volume, the heart rate and the load on the heart must be known, and a characteristic control curve or a regulating range must be selected. Cardiac behavior, and in particular the suitability of the stroke volume in the vicinity of the load limit as a control criterion, cannot be predicted. Numerous experiments have accordingly been necessary, to attain a suitable setting.